Crank arm hitting s...
 

Crank arm hitting stay

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I slapped a Shimano Hone Hollowtech crankset on a new 29" hardtail with a 73mm bottom bracket and 148mm stays, so boost wheels and the right crank arm shaves the chainstay on rotation under force.

Have I missed something here? I assumed this would just work or are pre-boost era cranks not compatible with modern frames?


 
Posted : 02/08/2023 1:55 pm
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You need a boost chainset.


 
Posted : 02/08/2023 1:56 pm
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Spacer on BB? at 73mm shouldn’t need one but I’ve bodged your issues like this. 2mm spacer hasn’t impacted tensioning the crank on, but gives a bit more clearance arm to frame.


 
Posted : 02/08/2023 1:58 pm
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That's an odd one. The boost part just really dictates where the chainring sits in the chainline. I would've imagined that a Hone crank was the same shape as every other Shimano HT2 crank and would've been fine. What frame is it? Just in case someone else has had a similar issue


 
Posted : 02/08/2023 1:59 pm
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+1 on using a spacer as a bodge.

Have you checked frame trueness? Could be wonky BB shell or off-centre or bent rear end.


 
Posted : 02/08/2023 2:04 pm
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@mashr it's an On One Huntsman


 
Posted : 02/08/2023 2:13 pm
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On One Huntsman

👇

Have you checked frame trueness?


 
Posted : 02/08/2023 2:16 pm
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@matt_outandabout that's possible, the frame was acquired from a local auction house cheaply so I assume it was a second or returned item. What exactly would I be checking and how to go about it


 
Posted : 02/08/2023 2:17 pm
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I had a similar problem on an expensive road frame. It was the frame. The stays hadnt been bent correctly before welding. Manufacturer replaced the frame.


 
Posted : 02/08/2023 2:21 pm
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Spacer on BB? at 73mm shouldn’t need one

A 73mm BSA BB still needs a spacer. 2.5mm on the drive side.

A 68mm uses 3 spacers. 2x drive side. 1x non driveside.

I've got an older SLX 3x crankset running on my Hello Dave. I just moved the chainring to the outer position. Works fine.


 
Posted : 02/08/2023 2:22 pm
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Yep as above, 73mm shimano BB should still have one spacer - a hangover from the old 'etype' BB mounted front derraileurs.

If you aint got one - the crank will touch the frame. If its fitted, but on the wrong side, your cranks are off centre, if its not fitted at all, then your cranks will have 2.5mm of side to side play in them.

Unless the frames bent, of course!


 
Posted : 02/08/2023 2:27 pm
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What exactly would I be checking and how to go about it

Can you run a taught string from L drop out / headtube / R drop out and see if it produces an equal gap between the string and the seat tube on each side?


 
Posted : 02/08/2023 2:28 pm
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A known good rear wheel - that puts the rim correctly on the centre line in another bike, would be a good thing to check.


 
Posted : 02/08/2023 2:31 pm
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Ok Yeah this was totally my mistake, I have added a 5mm spacer and all good now. For some reason I was convinced that at 73mm wide I didn't need one, not sure qhy I thought that now. It has been a while since I've done this sort of thing


 
Posted : 02/08/2023 7:13 pm
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2.5mm Shirley.


 
Posted : 02/08/2023 7:26 pm
binman and dc1988 reacted
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There was a thread on the On One Facebook page about the Huntsmans having chainstay clearance issues due to a design / manufacturing defect.

Planet X were refunding or exchanging frames under warranty.

Spacers will help, but it's not your cranks that are the issue. That batch of frames were dodgy.


 
Posted : 02/08/2023 8:31 pm
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That's really helpful, as I've noticed wear on my huntsman's chainstay where my crank has been rubbing. But not able to find the thread on the on-one Facebook page. Was it posted recently?


 
Posted : 17/08/2023 9:42 am
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Just found the thread on the on-one owners FB group 👍


 
Posted : 17/08/2023 7:42 pm